Initial experience using middle meningeal artery embolisation for patients with recurrent and high-recurrence-risk chronic subdural haematoma

Recurrence rates following surgical management of chronic subdural haematoma (CSDH) range from 5 to 33 %. There is growing evidence which suggests middle meningeal artery embolisation (MMAe) may reduce recurrence rates when used as surgical adjunct or standalone treatment. In this study we described our experience of this new procedure in the our UK institution. Patients with recurrent CSDH or CSDH at high risk of recurrence were selected for MMAe on a case-by-case basis following MDT discussion. A departmental database was used to identify patients treated. 26 CSDH were embolised in 20 patients; 9 CSDH were de-novo and 17 were recurrent. 10/26 CSDH were treated with MMAe only. No procedural mortality, access site or thrombo-embolic complications occurred. One patient experienced symptomatic collection growth 12 h following MMAe and required surgical drainage. 15 (75 %) of patients were living at home at follow-up (mean 14 months). On imaging follow-up 15/18 showed CSDH volume reduction or resolution, 1/18 remained stable requiring no further treatment, 2/18 patients suffered recurrent CSDH requiring treatment. In both recurrent cases incomplete embolisation was noted on procedural imaging (posterior division of MMA not embolised). Persistent posterior MMA division filling was significantly associated with collection recurrence (p = 0.002). Our results suggest MMAe as a stand-alone or adjuvant therapy can be performed safely in a UK neuroscience setting and is associated with high rates of symptomatic CSDH size reduction or resolution in problematic CSDH that have either recurred or are prone to recurrence.

Mechanical thrombectomy with Q catheter in stroke caused by primary and secondary distal and medium vessel occlusions

BACKGROUND

The MIVI Q aspiration catheters have been shown to achieve significantly greater flow rates than other intracranial aspiration catheters in vitro. We describe our initial real-world experience with the MIVI Q catheter in emergent acute ischemic stroke (AIS) caused by distal and medium vessel occlusions (DMVO).

METHODS

Data was collated from a prospectively maintained database which included patients from October 2019 to December 2022. Occlusion demographics, thrombectomy technique, reperfusion scoring, procedural complications and disposition were assessed. The primary outcome of interest was rate of successful reperfusion defined as thrombolysis in cerebral infarction (TICI) score 2b-3. Secondary outcomes included rate of first pass effect (FPE) and complications.

RESULTS

We included 64 target occlusions in 51 patients. The Q catheter successfully reached the DMVO in all occlusions. Successful reperfusion was achieved in 49/64 (76.6%) occlusions, and TICI scores were similar for primary and secondary DMVOs (P value = 0.41). FPE was achieved in 39/64 (60.9%) occlusions and did not differ between primary and secondary DMVOs (P value = 0.13). Reperfusion hemorrhage occurred in 3/64 (4.7%) cases, small volume subarachnoid hemorrhage in 3/64 (4.7%) cases, and small hemorrhagic transformation in 1/64 (1.6%) cases; the rate of complications did not differ based on primary versus secondary DMVO (P value = 0.29).

CONCLUSION

The MIVI Q catheter is both safe and effective. Our real-world experience supports the superior flow rates demonstrated in vitro and translates into high rates of successful reperfusion in AIS caused by DMVO in clinical practice.

pCONUS 2 and pCONUS 2-HPC in the treatment of wide-necked intracranial aneurysms: Multicentre UK experience

BACKGROUND/PURPOSE

pCONUS 2 and pCONUS 2-HPC are neck-bridging devices that provide coiling support in the endovascular treatment of wide-necked intracranial aneurysms. To date, limited multicentre data has been published. This study provides the first pooled data from multiple UK centres regarding outcomes for these devices covering the periprocedural period to 6-month follow-up.

MATERIALS/METHODS

This retrospective, single-arm study assessed 65 patients treated over 3 years from the time of procedure to 6 months post-procedure across four UK centres. Data collected included patient demographics, aneurysm characteristics and antiplatelet regimens. Outcome measures were angiographic results and procedure-related complications from the immediate periprocedural period to 6-month follow-up.

RESULTS

Fifty-four unruptured (83.1%) and 11 ruptured (16.9%) aneurysms were treated. Fifty-five aneurysms were located in the anterior circulation (87.7%). There were four device-related intraprocedural complications: three cases of asymptomatic, temporary thrombus formation and one mortality associated with branch vessel occlusion and aneurysm re-bleeding in a ruptured case. There were no post-procedural device-related complications. Satisfactory occlusion was achieved in 58/65 procedures (89.2%) at time of treatment and in 44/60 (73.3%) at 6 months. Satisfactory occlusion correlated with aneurysm size and coiling packing density. Retreatment was required for five unruptured cases (7.7%) and was straightforward with the device in situ.

CONCLUSION

pCONUS 2 and pCONUS 2-HPC have good short-term safety profiles. The use of pCONUS 2-HPC in the acute treatment of ruptured aneurysms with postprocedural SAPT is feasible. The devices have an intraprocedural complication rate of 4/65 (6.2%) across multiple UK centres, including a single death (1.5%).

Acute ECG changes in a woman presenting to coronary care with fluctuating consciousness

We present the case of a 67-year-old woman brought into the coronary care unit (CCU) with a suspected ST-segment elevation myocardial infarction (STEMI) due to lateral ST-segment elevation on her 12-lead electrocardiogram (ECG) and a significant troponin rise, but no reported chest pain and a fluctuating consciousness level. Whilst in CCU, she deteriorated further with a reduction in consciousness and sluggish pupillary reflexes, warranting urgent computed tomography (CT) of her brain, which confirmed extensive subarachnoid haemorrhage (SAH) with early evidence of hydrocephalus. She was therefore transferred to the local tertiary neurosurgical centre for endovascular coiling. ECG changes alongside a raised troponin are not uncommon findings in SAH and clinicians should exercise vigilance and consider urgent brain imaging in the absence of chest pain and presence of neurological deficit, to prevent adverse events from unnecessary antiplatelet or anticoagulant therapy, and invasive coronary angiography. SAH is a medical emergency and prompt recognition and referral for neurosurgical intervention is integral for optimal patient outcome.

Endovascular treatment for vaccine-induced cerebral venous sinus thrombosis and thrombocytopenia following ChAdOx1 nCoV-19 vaccination: a report of three cases

BACKGROUND

Vaccine-induced thrombosis and thrombocytopenia (VITT) is a rare complication following ChAdOx1 nCoV-19 vaccination. Cerebral venous sinus thrombosis (CVST) is overrepresented in VITT and is often associated with multifocal venous thromboses, concomitant hemorrhage and poor outcomes. Hitherto, endovascular treatments have not been reviewed in VITT-related CVST.

METHODS

Patient records from a tertiary neurosciences center were reviewed to identify patients who had endovascular treatment for CVST in VITT.

RESULTS

Patient records from 1 January 2021 to 20 July 2021 identified three patients who underwent endovascular treatment for CVST in the context of VITT. All were female and the median age was 52 years. The location of the CVST was highly variable. Two-thirds of the patients had multifocal dural sinus thromboses (sigmoid, transverse, straight and superior sagittal) as well as internal jugular vein thromboses. Intracerebral hemorrhage occurred in all patients; subarachnoid blood was noted in two of them, and intraparenchymal hemorrhage occurred in all. There was one periprocedural parenchymal extravasation which abated on temporary cessation of anticoagulation. Outcome data revealed a 90-day modified Rankin Scale (mRS) score of 2 in all cases.

CONCLUSIONS

We demonstrate that endovascular treatment for VITT-associated CVST is feasible and can be safe in cases that deteriorate despite medical therapy. Extensive clot burden, concomitant hemorrhage, rapid clinical progression and persistent rises in intracranial pressure should initiate multidisciplinary team discussion for endovascular treatment in appropriate cases.

Aortic and supra-aortic arterial tortuosity and access technique: Impact on time to device deployment in stroke thrombectomy

BACKGROUND

Longer intervals to reperfusion in patients treated with mechanical thrombectomy (MT) for emergent large vessel occlusion (ELVO) stroke are associated with worse outcomes and influenced by the operator's ability to navigate individual anatomy. Our aims were to assess the impact of time from puncture to first deployment of the MT device (DT) on technical and clinical outcomes, develop an Anatomical Assessment for Mechanical Thrombectomy Score (ASMETS) that could predict DT and assess how different methods of intracranial access (coaxial-direct or exchange) influence this.

METHODS

Retrospective review of a prospective database of patients treated with MT for ELVO between November 2015 and August 2018. CTAs were assessed for ASMETS. Intracranial access technique was at the discretion of the operator. Technical and clinical outcomes and complications were recorded. Linear and logistic regression analysis was performed.

RESULTS

92 patients were included. The impact of DT on clinical outcomes was significant. An unfavourable ASMET score is significantly associated with longer DT (p = 0.002) and linear regression showed DT time can be predicted by ASMETS - F(1,90) = 6.182, p = 0.015. No difference was demonstrated between different access techniques.

CONCLUSION

CTA-based ASMETS can predict time between arterial puncture and deployment of the mechanical thrombectomy device in stroke patients, irrespective of the technique used to catheterise the target ICA. This could inform the operator in preparing appropriate strategies to overcome challenging vascular anatomy in patients undergoing MT.

Mechanical thrombectomy for acute ischaemic stroke during the COVID-19 pandemic: changes to UK practice and lessons learned

AIM

To describe evolving practices in the provision of mechanical thrombectomy (MT) services across the UK during the COVID-19 pandemic, the responses of and impact on MT teams, and the effects on training.

MATERIALS AND METHODS

The UK Neurointerventional Group (UKNG) and the British Society of Neuroradiologists (BSNR) sent out a national survey on 1 May 2020 to all 28 UK neuroscience centres that have the potential capability to perform MT.

RESULTS

Responses were received from 27/28 MT-capable centres (96%). Three of the 27 centres do not currently provide MT services. There was a 27.7% reduction in MTs performed during April 2020 compared with the first 3 months of the year. All MT patients in 20/24 centres that responded were considered as COVID-19 suspicious/positive unless or until proven otherwise. Twenty-two of the 24 centres reported delays to the patient pathway. Seventeen of the 24 centres reported that the COVID-19 pandemic had reduced training opportunities for specialist registrars (SpR). Fourteen of the 24 centres reported that the pandemic had hampered their development plans for their local or regional MT service.

CONCLUSION

The present survey has highlighted a trend of decreasing cases and delays in the patient pathway during the early stages of the COVID-19 pandemic across UK centres.

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National UK MT service survey during COVID-19 lockdown.

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Decline in MTs.

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Delays to patient journey.

Validation studies of virtual reality simulation performance metrics for mechanical thrombectomy in ischemic stroke

INTRODUCTION

Mechanical thrombectomy (MT) has transformed the treatment of ischemic stroke. However, patient access to MT may be limited due to a shortage of doctors specifically trained to perform MT. The studies reported here were done to (1) develop, operationally define, and seek consensus from procedure experts on the metrics which best characterize a reference procedure for the performance of an MT for ischemic stroke and (2) evaluate their construct validity when implemented in a virtual reality (VR) simulation.

METHODS

In study 1, the metrics for a reference approach to an MT procedure for ischemic stroke of 10 phases, 46 steps, and 56 errors and critical errors, were presented to an international Delphi panel of 21 consultant level interventional neuroradiologists (INRs). In study 2, the metrics were used to assess 8 expert and 10 novice INRs performing a VR simulated routine MT procedure.

RESULTS

In study 1, the Delphi panel reached consensus on the appropriateness of the procedure metrics for a reference approach to MT in ischemic stroke. Group differences in median scores in study 2 demonstrated that experienced INRs performed the case 19% faster (P=0.029), completed 40% more procedure phases (P=0.009), 20% more steps (P=0.012), and made 42% fewer errors (P=0.016) than the novice group.

CONCLUSIONS

The international Delphi panel agreed metrics implemented in a VR simulation of MT distinguished between the computer scored procedure performance of INR experts and novices. The studies reported here support the demonstration of face, content, and construct validity of the MT metrics.

A systematic review and meta-analysis of observational evidence for the use of bailout self-expandable stents following failed anterior circulation stroke thrombectomy

BACKGROUND

The crucial role of thrombectomy in the management of emergent large vessel occlusive stroke is not disputed but there is a technical failure rate in a significant minority of patients whose outcomes are often poor. Our objective was to perform a systematic review and meta-analysis to assess the safety and efficacy of permanent self-expandable stent deployment as a bailout procedure in cases of failed anterior circulation thrombectomy.

METHODS

Two independent reviewers searched the Pubmed (Medline) database for studies reporting outcomes following failed endovascular thrombectomy with subsequent rescue therapy employing self-expandable stents.

RESULTS

Eight studies (one prospective, seven retrospective) originating from Europe, Asia, and America comprising 160 patients met the inclusion criteria. Estimated baseline National Institutes of Health Stroke Scale score was 17.1 (95% CI 15.7 to 18.4). Following failed thrombetcomy and stent deployment, the rate of favorable outcome (modified Rankin Scale score 0-2) was 43% (95% CI 34% to 53%). Pooled mortality was 21% (95% CI 13% to 33%). Successful recanalization (Thrombolysis in Cerebral Infarction (TICI) 2b-3 or Thrombolysis in Myocardial Infarction (TIMI) 2-3) was 71% (95% CI 63% to 77%). Symptomatic intracerebral hemorrhage was seen in 12% (95% CI 7% to 18%). The Solitaire stent (Medtronic) was the most commonly deployed stent following failed thrombectomy attempts (66%; 95% CI 31% to 89%). Pre- or post-stent angioplasty was performed in 39%of patients (95% CI 29% to 48%). Glycoprotein IIb/IIIa inhibitors were used in 89% (95% CI 71% to 97%). 95% of patients received postprocedural antiplatelet therapy.

CONCLUSION

A rescue stent procedure seems reasonable as a last resort following failed thrombectomy but currently the level of evidence is limited. Prospective registries may aid in guiding future recommendations.

Safety profile of an 8F femoral arteriotomy closure using the Angio-Seal device in thrombolysed acute stroke patients undergoing thrombectomy

Background The relationship between bridging thrombolysis and femoral access site complications after mechanical thrombectomy remains contested. Use of a closure device could minimise bleeding complications. This study aimed to elucidate the rate of access site complications in a cohort of patients treated using an 8F groin sheath with subsequent closure using the Angio-Seal to assess safety and the impact of bridging thrombolysis on access site complication rate. Methods All patients with large vessel occlusive stroke treated between 2014 and 2017 with thrombectomy with or without bridging thrombolysis were reviewed. A prospectively acquired departmental database was used to obtain baseline data, and the radiology information and haematology reporting systems were used to record imaging or transfusion relating to subsequent access site complications. Results Seventy-five patients treated with thrombectomy alone were compared to 70 patients treated with prior intravenous thrombolysis. All had an 8F femoral sheath placed for arterial access, and all underwent attempted haemostasis with an 8F Angio-Seal. Two patients (1.14%) suffered Angio-Seal device failure necessitating manual pressure. One patient (0.6%) suffered a small femoral pseudo-aneurysm. No retroperitoneal haemorrhage, haematoma requiring transfusion, ipsilateral deep-vein thrombosis or ipsilateral acute limb ischaemia was encountered. There was no significant difference in the rate of haemorrhagic, ischaemic or infective complications between those treated with bridging thrombolysis or thrombectomy alone. Conclusion Use of the Angio-Seal closure device for 8F femoral access is safe in acute stroke patients. Intravenous thrombolysis prior to endovascular thrombectomy does not significantly alter femoral access site complication rate if this approach is used.

Cervical ICA pseudo-occlusion on single phase CTA in patients with acute terminal ICA occlusion: what is the mechanism and can delayed CTA aid diagnosis?

Background

Single-phase CT angiography (CTA) forms the basis of hyperacute stroke imaging but many patients with terminal internal carotid artery (ICA) occlusion exhibit a pseudo-occlusion of the cervical ICA whereby a column of unopacified blood mimics a tandem cervical ICA lesion. We aimed to investigate the utility of a delayed phase acquisition to aid identification of a pseudo-occlusion and investigated the mechanism for this imaging artefact.

Methods

Thirteen patients with a pseudo-occlusion were compared with 13 patients without. CT, CTA, and digital subtraction angiographic images were reviewed by two interventional neuroradiologists for extension of thrombus into the ophthalmic segment, filling of the posterior communicating artery and ophthalmic artery, and for extension of contrast beyond the cervical segment and outline of the proximal clot surface by contrast on delayed imaging performed at 40 or 80 s.

Results

Those with a pseudo-occlusion demonstrated more frequent thrombus extension into the ophthalmic segment (100% vs 23%, P=0.0001), less frequent filling of the posterior communicating artery (15% vs 85%, P=0.0012), and less frequent filling of the ophthalmic artery (15% vs 92%, P=0.0002) compared with those without a pseudo-occlusion. Delayed CTA imaging showed contrast beyond the cervical segment and meeting the proximal clot face in 2/11 patients. Each of these two patients showed patency of the posterior communicating artery origin.

Conclusion

Thrombus extension into the ophthalmic segment and patency of the posterior communicating artery and ophthalmic artery seem to govern whether a patient with a terminal ICA occlusion exhibits a pseudo-occlusion. Delayed imaging was of limited value in identification of a pseudo-occlusion.

Characteristics of pain in hospitalized medical patients, surgical patients, and outpatients attending a pain management centre

BACKGROUND

The characteristics and psychological impact of pain suffered by medical inpatients has been relatively under-investigated. The aim of this study was to compare the pain experience of medical, surgical inpatients, and patients attending a pain management centre. Some aspects of the quality of pain scoring and prescribing were also audited.

METHODS

Medical inpatients with significant pain (moderate or severe pain on a verbal rating scale) were assessed using a battery of psychometric questionnaires. Comparator samples of surgical inpatients and patients attending the pain management centre were recruited.

RESULTS

The prevalence of significant pain did not differ between the medical group (n=37) and the surgical group (n=38) (16.7% and 19.9%). Chronic pain was common in the medical group (54%) and the surgical group (50%). There were no differences in psychometric variables between the medical and surgical groups. Clinically significant scores for anxiety and depression (HADS ≥11) were common in all groups (30-38%). There was less concordance between patient-reported pain scores and nurse-recorded pain scores in the medical group than the surgical group and analgesic prescribing differed between the two groups.

CONCLUSIONS

The characteristics of pain in the medical and surgical groups were similar, with high levels of anxiety and depression. The pain management group differed from the inpatient groups, with higher levels of psychopathology and poorer coping. These findings provide some insight into the complex nature of pain in hospital inpatients, and may inform where limited resources should be utilized to provide greatest patient benefit.

The reliability and validity of general psychotic rating scales with people with mild and moderate intellectual disabilities: an empirical investigation

BACKGROUND

Whilst assessment tools have been developed to diagnose schizophrenia in people with mild intellectual disabilities (IDs), little attention has been paid to developing reliable and valid dimensional measures of psychotic experiences with this population. This study investigates the reliability and validity of two such measures developed for the general adult psychiatric population, the Positive and Negative Syndrome Scale (PANSS) and the Psychotic Symptom Rating Scales (PSYRATS), with a population of adults with mild IDs.

METHOD

Sixty-two adults with mild IDs were interviewed using the PANSS and PSYRATS, and independently interviewed using the Psychiatric Assessment Schedule--Adults with Developmental Disability (PAS-ADD) to obtain psychiatric diagnoses to the criteria of the International Classification of Diseases--Tenth Revision (ICD-10). On the basis of ICD-10 diagnosis, participants were divided into three groups: psychosis (n=11); other mental health problem (n=14); no mental health problem (n=37). PANSS and PSYRATS subscale scores were compared across these three groups and were correlated with PAS-ADD symptom scores across a number of PAS-ADD symptom domains.

RESULTS

All PANSS and PSYRATS subscales showed adequate internal reliability, largely good test-retest reliability, and logical inter-correlations between subscales. The PANSS positive symptoms and the PSYRATS auditory hallucinations subscales differentiated between the psychosis group and the other groups; the PANSS general symptoms subscale differentiated between the psychosis and no mental health problem groups; and the PANSS negative symptoms and the PSYRATS delusions subscales did not differentiate between the three groups.

CONCLUSIONS

The PANSS and PSYRATS are promising measures for use with people with mild IDs and psychotic experiences, although further investigation of items relating to negative symptoms and delusions is warranted.

Permanent vegetative state: usefulness and limits of a prognostic definition

Jennett and Plum's 1972 naming of post-coma unresponsiveness as "persistent vegetative state (PVS)" characterised the condition as essentially irrecoverable and insentient. The evidence for these propositions was always weak, and they have been largely disproved by more recent research. Nonetheless, the definition and the attitudes it embodies remain generally accepted, resting as they do on a firm foundation of medical attitudes to disability and a public eagerness to evade uncomfortable facts. The first step in altering our approach to people with this form of communication impairment must be to rectify our understanding of the terminology.

Remediation of communication problems through facilitated communication training: a case study

Facilitated communication training (FCT) is an educational technique intended to allow people who cannot speak or sign fluently to develop the hand skills necessary to use other non-speech communication strategies. It involves support to the arm, wrist or hand of the student, who is thus enabled to control his pointing, and has recently been the subject of considerable debate. Critics of the technique have cast doubt on the existence of any language problem remediable by touch. This study discusses the case of a person who had a language problem that did not appear to be connected with overt neuromotor impairment, was not accompanied by behavioural disturbance, and was remediable by touch alone. The case raises some interesting questions about the relation of physical prompts to language use.

Synthesis and antiinflammatory activity of certain 5,6,7,8-tetrahydroquinolines and related compounds

Modification of some 8-benzylidene-5,6,7,8-tetrahydroquinolines, which have good antiulcer activity, led to three distinct classes of compounds with good in vivo antiinflammatory activity. Initial efforts led to a series of alkenes derived from 5,6,7,8-tetrahydroquinolines substituted at the 8-position. A second approach concentrated on replacing the CH linkage of these 8-benzylidene-substituted compounds with other spacer groups and increasing the size of the cycloalkyl ring from a six- to seven-membered ring, which provided 6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridine analogues. Finally, the substituent was switched from the cycloalkyl ring to the 2-position of the pyridine ring. Variation of the 2-substituent was also examined. Optimal antiinflammatory activity after oral administration was found in both the rat carrageenan paw edema and rat developing adjuvant arthritis models with 2-substituted 6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridines, and of particular interest was 27 (WY-28342).

The essential bacterial cell-division protein FtsZ is a GTPase

Cytokinesis defines the last stage in the division cycle, in which cell constriction leads to the formation of daughter cells. The biochemical mechanisms responsible for this process are poorly understood. In bacteria, the ftsZ gene product, FtsZ, is required for cell division, playing a prominent role in cytokinesis. The cellular concentration of FtsZ regulates the frequency of division and genetic studies have indicated that it is the target of several endogenous division inhibitors. At the time of onset of septal invagination, the FtsZ protein is recruited from the cytoplasm to the division site, where it assembles into a ring that remains associated with the leading edge of the invaginating septum until septation is completed. Here we report that FtsZ specifically binds and hydrolyses GTP. The reaction can be dissociated into a GTP-dependent activation stage that is markedly affected by the concentration of FtsZ, and a hydrolysis stage in which GTP is hydrolysed to GDP. The results indicate that GTP binding and hydrolysis are important in enabling FtsZ to support bacterial cytokinesis, either by facilitating the assembly of the FtsZ ring and/or by catalysing an essential step in the cytokinetic process itself.

Immunocytochemical differentiation of microtubules in the cytoskeleton of Giardia lamblia using monoclonal antibodies to alpha-tubulin and polyclonal antibodies to associated low molecular weight proteins

In interphase trophozoites of Giardia lamblia, separate populations of microtubules constitute the four parts of the mastigont apparatus: flagella, ventral disc, funis and median body. Antigenic differences between the tubules have been investigated by light and electron immunocytochemistry after labelling with two monoclonal antibodies to alpha-tubulin (YL 1/2 and YOL 1/34 clones), and with polyclonal antibodies to Giardia tubule-associated proteins. Both anti-tubulins stained all tubules after isolated structures were fixed in formaldehyde, but different patterns of reactivity were shown by unfixed tubules. YL 1/2 antibodies labelled flagellar axonemes and basal bodies, funis and median body tubules. Disc microtubules were mostly unlabelled, but the antibody bound strongly to the outer edge of the disc where the ends of tubules are embedded. YOL 1/34 antibodies stained disc tubules uniformly, and cross-reacted with the median body but not with tubules of axonemes, basal bodies or funis. Antibodies to giardins 14A and 14B (approximately 30 000 Mr filament-forming proteins) localized these proteins in the microribbons attached to disc microtubules. The median body was also labelled by anti-giardins, indicating an ontogenetic relationship between this organelle and the ventral disc. A second set of approximately 30 000 Mr proteins with no immunoreactivity to anti-giardin was found in flagella purified without removing flagellar membranes. These polypeptides were Triton-soluble and therefore probably originated from an extra-axonemal site. A rabbit antiserum to the labile flagellar proteins specifically stained the two ventral flagella, but not the other six flagella on this cell.

Assembly of 2.5 nm filaments from giardin, a protein associated with cytoskeletal microtubules in Giardia

The giardins are a family of approximately 30000 Mr structural proteins found in microribbons attached to microtubules in the disc cytoskeleton of Giardia. After examining the solubility of giardins in various agents, a method has been developed to extract these polypeptides and subsequently precipitate them selectively. The giardin chains are soluble in 10 mM-HEPES/EDTA buffer at high pH and low ionic strength, but become insoluble in 10 mM-MES/EDTA buffer at pH 6.7 when the ionic strength is raised above 50 mM salt. By dialysing giardin extracts in turn against dissociating and reassembly buffers, the purification is obtained of a subset of giardin chains identified by sodium dodecyl sulphate/polyacrylamide gel electrophoresis as the cytoskeleton bands 14a, 14b and 15. The structures forming under assembly conditions are all composed of fine filaments, 2–3 nm in diameter. Filaments after the first cycle of assembly are found in bundles, narrow ribbons of two or three filaments, and large ordered tactoids. Assembly after a second cycle of solubilization yields a more uniform population of long ribbons. Both the tactoids and the second cycle ribbons are transversely banded at the 15 nm interval characteristic of microribbons in the cytoskeleton. Filaments in the tactoids are precisely placed at a centre-to-centre separation of 2.5 nm. Other structural features of the tactoids are discussed in relation to the association behaviour and possible dimensions of the giardin molecular subunit.

Selective extraction with Sarkosyl and repolymerization in vitro of cytoskeleton proteins from Giardia

Sarkosyl has been used to dissociate structures in cytoskeletons isolated from Giardia lamblia. Results from sodium dodecyl sulphate/polyacrylamide gel electrophoresis and from electron microscopy of insoluble residues show that the solubilization of components is partly selective. At low concentrations of detergent (less than 0.3%), microribbons and microtubules of the disc cytoskeleton disappear, but doublet microtubules from axonemes resist extraction. Consequently, the microribbon protein giardin is extracted into solution more completely than tubulin. Soluble proteins in 0.1% Sarkosyl have been fractionated by gel filtration chromatography in Bio-Gel P300. Giardin elutes in two positions: as a low molecular weight subunit, and in early fractions corresponding to a larger particle size in which subunits might be forming oligomers. Supernatants prepared in 0.5% Sarkosyl were diluted with 0.1 M-KCl or 0.1 mM-MgCl2 to bring about reaggregation of the cytoskeleton proteins. Reassembled structures seen in negatively stained preparations were polymorphic. Some tubulin ribbons of 5 nM protofilaments were identifiable' also there were large fibres and some flat sheets of very thin filaments. Electron micrographs of sheets have been analysed by optical diffraction. The transforms show that the lateral separation of the fine filaments is about 2.5 nm. Axial periodicities from features spaced along filaments were weak. A 3.75 nm layer-line has been detected, corresponding to a similar periodicity found earlier in microribbons.

Characterization of proteins from the cytoskeleton of Giardia lamblia

Proteins from the axonemes and disc cytoskeleton of Giardia lamblia have been examined by sodium dodecyl sulphate/polyacrylamide gel electrophoresis. In addition to tubulin and the 30 X 10(3) molecular weight disc protein, at least 18 minor components copurify with the two major proteins in Triton-insoluble structures. The most prominent minor bands have the apparent molecular weights of 110 X 10(3), 95 X 10(3) and 81 X 10(3). Protein of 30 X 10(3) molecular weight accounts for about 20% of organelle protein on gels. In continuous 25 mM-Tris-glycine buffer it migrates mostly as a close-spaced doublet of polypeptides, which are here given the name giardins. Giardia tubulin and giardin have been purified by gel filtration chromatography in the presence of sodium dodecyl sulphate. Well-separated fractions were obtained that could be further characterized. Both proteins are heterogeneous when examined by isoelectric focusing. Five tubulin chains were detected by PAGE Blue 83 dye-binding after focusing in a broad-range ampholyte gel. Giardin is slightly less acidic than tubulin. On gels it splits into four major and four minor chains with isoelectric points in the pI range from 5.8 to 6.2. The amino acid composition of the giardin fraction has been determined, and compared to Giardia tubulin and a rat brain tubulin standard. Giardins are rich in helix-forming residues, particularly leucine. They have a low content of proline and glycine; therefore they may have extensive alpha-helical regions and be rod-shaped. As integral proteins of disc microribbons, giardins in vivo associate closely with tubulin. The properties of giardins indicate that in a number of respects - molecular size, charge, stoichiometry - their structural interaction with tubulin assemblies will be different from other tubulin-accessory protein copolymers studied in vitro.

Preliminary methodology for controlled cost-benefit study of drug impact: the effect of cimetidine on days of work lost in a short-term trial in duodenal ulcer

The phase II/III U.S. clinical drug trials for cimetidine (Tagamet) in duodenal ulcer were examined for their potential application to cost-benefit analysis. Data on "time lost from work" were obtained from a special protocol added to these short-term, double-blind trials of cimetidine. Sixty-four outpatients from the clinical trials remained from an original pool of 217 after exclusion of those subjects who were either retired, unemployed, or of uncertain employment status. Cimetidine was significantly more effective than placebo in reducing "time lost from work" during ulcer disease. The patients' "time lost from work" occurred as a strikingly all-or-nothing phenomenon. We conclude that a prospective clinical trial is appropriate for gathering economic data.

5,6,7,8-Tetrahydroquinolines. 5. Antiulcer and antisecretory activity of 5,6,7,8-tetrahydroquinolinethioureas and related heterocycles

A series of thioureas derived from 5,6,7,8-tetrahydroquinoline, 1,5-, 1,6-, and 1,8-naphthyridiness, pyrido[2,3-b]azepine, and 7-azaindoline has been prepared and tested for antisecretory activity in the pylorus-ligated rat and protective activity against gastric erosions caused by cold-restraint stress. The thioureas exhibit different structure-activity relationships from the corresponding 5,6,7,8-tetrahydroquinoline-8-thiocarboxamides and these relationships are discussed. The activity of the thioureas is less affected by structural differences than the corresponding thioamides although they probably have the same mode of action.

5,6,7,8-Tetrahydroguinolines. 4. Antiulcer and antisecretory activity of 5,6,7,8-tetrahydroquinolinenitriles and -thioamides

A number of 5,6,7,8-tetrahydroquinoling-8-nitriles and -8-thioamides and related compounds have been found to be potent inhibitors of basal gastric secretion in the pylorus-ligated rat and to afford protection against gastric erosions induced in rats by cold-restraint stress. Molecular manipulation has proved useful in determining factors necessary for such activity and structure-activity relationships are discussed. It has been shown that the most necessary requirements for activity are a pyridine nitrogen with its available lone pair and a primary or secondary thioamide. Also desirable is a six-membered carbocyclic ring with relative freedom from steric hinderance around the 8 position.